fix: handle invalid static path encoding

[rissrice2105-agent]

Summary

• catch malformed percent-encoded static paths in the CommandBoard PWA server
• return 400 Invalid path encoding instead of allowing URIError to terminate the process
• preserve normal API/health handling after the bad request

Closes #35

Testing

• npm test
• npm run build
• manual server check: curl --path-as-is http://127.0.0.1:43173/% returns 400, then /health returns 200 and the process remains alive

npm run test:e2e --workspace @logicsrc/commandboard-web could not run because the local Playwright Chromium binary is not installed.